Solvent extraction



, atoms. Ipropose Patented Nov. 21, 1944 'UNlTED uST-ATES- PA NT Armand J. de Rosset,;Chicago, I ll,.,

Universal Oil Products Company,

assignor to Chicago,

a corporation of Delaware No Drawing.

This invention relates specifically to the separation of normally gaseous parafilns from normally gaseous olefins by means of a selective solvent.

It is often desirable to separate from a composite feed gaseous parafiins and gaseous olefins of the same number of carbon atoms, since there ar a great many processes in which a gas predominantly olefinic 'or parafilnic in character is required. For example, in thecatalytic sulfuric acid alkylation process alkylated by butylenes to form octanes, it is desirable that the feed gas to the process possess a relatively high ratio of iso-butane to olefin,

since in this manner a more selective reaction 'may be effected. On the other hand, for the polyin which iso-butan'e is merization of C3 and C4 olefins, and particularly for the selective polymerization of C4 oleflns in heat exchange reactors; it is often 7 have olefin contents as high as 50%. Therefore,

in order to prepare charging stocks of such widely different composition from cracking plant gases, it isnecessary to have a means of paraflins from the olefins. I

I have discovered that aliphatic amino alcohols exhibit a far greater solubility for the normally the same. number of carbon therefore to use the liquid members of this series as selective solvents for the separation of normally gaseous paraflins from olefins. V

In one specific embodiment this invention relates to a processfor the separation of normally gaseous oleflns from normally gaseous paraflins parafllns having which comprises contacting a composite charge with an aliphatic amino alcohol, separatin the,

desirable to jcharacterized v one amino group and at least i separating the V gaseous oleflns than for the normally gaseous Application October 17, 1941, Serial N0. 415,451

o Hit-C in x i'ifoil -c in o 11 Ethyl ethanol amine HOCH2-Cli1 N-oH'rcul -om -cm H0--'CH9-CH5 n-l3utyl diethauol amine imoHr-Cm N-cui-oin HO-CHz-CH: I

Ethyl dietlianol amino CH1; I v

omnpomou 7 CH: I

2-meth yl {I -a mi no prol dill-3%)] Each of the above compounds is liquid at room temperature and each is fairly stable. Furthermore, each compound contains at least one amino group and at least one hydroxyl group.

I have also observed that, as a rule, the selec tive solvent action of the atoms attached to a nitrogen atom is decreased.

For this reason an alcohol having a primary amino group attached is usually more selectivev than one having only a secondary amino group,

' having only a tertiary amino group. This bethe latter in turn .being'more selective than one havior on the part of these compounds may possibly be ex'plalned'in theory, at least, by an aflinity for olefini-c bonds exerted by the hydrogen atom attached to the'nitrogen atom. Therefore, alcohols having primary or secondary amino groups are preferred. In some cases substituted amino alcohols, having a group such as an aryl radical, halogen radical, etc. linked to the aliphatic chain. may be employed as the solvents for this process.

.- Ordinarily, however, the unsubstituted amino "alcohols are preferred because of their relative ease of manufacture, their lower molecular weight. etc.

although the normally gaseoushydrocarbons may be treated either in the'vapor or in the liquid phase. According to one mode of operation, when the hydrocarbons are in the vapor phase, the latter are passed upward through an absorber countercurrently to the solvent. the lean or raffinate being withdrawn from the top of ,the absorber and the rich liquid or extract/from the bottom. Thereafter the extract may be heated and flashed or treated in any other suitable manner to separate the desired concentrated olefinic fraction from the solvent. The solvent may then amino alcohols toward 1 olefins decreases as the number of hydrogen.

The solvents are employed in the liquid phase. a

be returned to the top of the absorber to complete the cycle. Liquid phaseoperation, that is,- operation in which two liquid phases are present with or without the presence of a vapor phase, may also be employed. In either the vapor or the liquid phase operation,- more than one extraction stage may be used, if desired. In-any event, the raflinate is richer in paraflins and the extract richer in olefins than the composite feed.

2,368,298 I r v that in cases where the solvent is relatively nonvolatile and where the liquid phase solubilities are not very high, this pressure is approximately the sameas the vapor pressure of the pure hydrocarbon at the temperature of the experiment. Furthermore, thispressure is the only pressure at 1 which these three phases may exist, according to stant) the phase rule (when the temperature is con- In this table the solubility c is expressed The following data are given to show the soluas the volume of gaseous hydrocarbon (reduced bilities of variou gaseous hydrocarbonsin some a to 0 C. and760 mm.) dissolved in a unit volume of the above solvents. InTables 11,111 and IV of the solvent at 25 C. and at the pressure of solubilities obtained by contacting the purehy- .the experiment. drocarbon in the vapor state with several of the I 7 TABLE V liquid solvents of the aliphatic amino alcohol type i are presented. In these tables the solu'bilities Llqmd phase -w extraction are expressed in terms of the Bunsen coefllcient 0:. m This coeflicient is defined as the volume'of-gas dise 5mm solved (corrected to 760 mm. pressure and 0 C.) per unit volume of solvent at the temperature of 2 Ethanol 'gfigi?" th experiment, in this case 0., when the,par- Hwmmbpn amine ethylene m1 pressure of the gas is 760 mm. 11mm TABLE II a Solubility at 25 (a, c Solvent-ethanol amine. Vapor phase solvent 25 v extraction 1 3422331:11:31:;33:3323;131:131:2:: 331% 131%? Hydrocarbon iggPgfi v Itis apparent from the above data that in every case the solubility of the olefin, whether Ethane M3 in the vapor or theliquid phase, is considerably EthylezijjjjIIIIIIIT'" 0.36 greater than that of the paraflin. These solvents .3 are therefore highly suited for a separation of ropylene O. 82 n Butane o 97 normally gaseous parafiins from normally. gase- 2 11 (ms olefins. It] is also evident from the data,

however, that the solvents are not strictly equiv- TABLE III alent. Solvent-hydroryethyl ethylene diamine. Vapor AlPhough this inventign been directed wphas solventemtmction, marily toward the separation of normally gaseous paramns from olefins, it is not to be unduly 11msolubility ited thereto since other types of normally gaseous H dr at hydrocarbons may also be separated by these solvents. For example, the solvents may be em- Ethan-e 7 ployed in the separation of normally gaseous g mparaflins from diolefins or acetylenes as well as ropane 0.67 Propylene- 0.74 In the separation of normally gaseous mono- -g igg g3 olefins from the corresponding diolefins or acety- 7 1 ienes. a r I claim as my invention: TABLE IV 11. A process for separating normally gaseous o efins from normally gaseous parainns in a hy- Solvent 2 gizgz i gy g ggfig Y4 drocarbon mixture containing the same, which comprises treating said mixture with a suflicient 8 mm V quantity of hydroxyethyl ethylene diamine to Hy r c r f f, form an olefin-rich extract and a paraffin-rich rafllnate, and separately recovering said extract n-Butane S. 14 and a r l-butelw 11-86 A process for separating normall gaseous olefins from normally gaseous paraflins in a hy- Table V below' shows the solubilities of the drocarbon mixture containing the same, which hydrocarbons as determined by contacting the comprises treating said mixture with a selective pure hydrocarbon in the liquid phase at 25 C. solvent consisting essentially" of hydroxyethyl at the pressure at which three separate phases ethylene diamine to form an olefin-rich fraction exist, namely, a hydrocarbon in solvent phase, and a paraflin-rich fraction, and separately rea solvent in hydrocarbon phase; and a vapor covering said fractions.

phase, principally hydrocarbon. vIt is evident .ARMAND J DE ROSSET. 

